U.S. patent number 10,360,828 [Application Number 15/399,284] was granted by the patent office on 2019-07-23 for application processor and display device including the same.
This patent grant is currently assigned to SAMSUNG DISPLAY CO., LTD.. The grantee listed for this patent is SAMSUNG DISPLAY CO., LTD.. Invention is credited to Cheol-Hwan Eom, Sang-Myeon Han, Sun-Joon Hwang, Dong-Hak Pyo.
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United States Patent |
10,360,828 |
Pyo , et al. |
July 23, 2019 |
Application processor and display device including the same
Abstract
An application processor includes a scaling rate calculator that
determines a scaling rate of first image data based on stress data
that includes pixel degradation information for each pixel; and an
image processor that generates second image data by decreasing a
maximum grayscale value of the first image data based on the
scaling rate, where the first image data is received from an
external component.
Inventors: |
Pyo; Dong-Hak (Hwaseong-si,
KR), Eom; Cheol-Hwan (Hwaseong-si, KR),
Han; Sang-Myeon (Hwaseong-si, KR), Hwang;
Sun-Joon (Cheonan-si, KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
SAMSUNG DISPLAY CO., LTD. |
Yongin-si, Gyeonggi-do |
N/A |
KR |
|
|
Assignee: |
SAMSUNG DISPLAY CO., LTD.
(Yongin-si, Gyeonggi-Do, KR)
|
Family
ID: |
59314656 |
Appl.
No.: |
15/399,284 |
Filed: |
January 5, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170206819 A1 |
Jul 20, 2017 |
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Foreign Application Priority Data
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Jan 19, 2016 [KR] |
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10-2016-0006343 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G09G
3/2011 (20130101); G09G 3/006 (20130101); G09G
3/3225 (20130101); G09G 3/2092 (20130101); G09G
2360/16 (20130101); G09G 5/06 (20130101); G09G
2320/045 (20130101); G09G 2330/12 (20130101); G09G
2320/0295 (20130101); G09G 2320/0285 (20130101); G09G
2320/0233 (20130101) |
Current International
Class: |
G09G
3/00 (20060101); G09G 3/3258 (20160101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1020110014185 |
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Feb 2011 |
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KR |
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1020150076783 |
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Jul 2015 |
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KR |
|
Primary Examiner: Chow; Jeffrey J
Attorney, Agent or Firm: F. Chau & Associates, LLC
Claims
What is claimed is:
1. An application processor comprising: a scaling rate calculator
that determines a scaling rate of first image data based on stress
data that includes pixel degradation information for each pixel,
wherein the first image data is received from an external
component; and an image processor that generates second image data
by decreasing a maximum grayscale value of the first image data
based on the scaling rate.
2. The application processor of claim 1, wherein the scaling rate
calculator calculates the scaling rate of the first image data
based on the pixel degradation information and a look-up table, and
wherein the look-up table includes the scaling rate, and the
scaling rate is predetermined based on the pixel degradation
information.
3. The application processor of claim 2, wherein the lookup table
further includes a compensation grayscale value which is calculated
based on an input grayscale value of the first image data and the
pixel degradation information, and wherein the scaling rate is
greater than or equal to a ratio of the input grayscale value to
the compensation grayscale value, wherein the compensation
grayscale value is equal to a maximum grayscale value that is
usable in the second image data.
4. The application processor of claim 2, wherein the sealing rate
calculator selects maximum pixel degradation information from a
maximum stress data value, and calculates the scaling rate of the
first image data based on the maximum pixel degradation
information.
5. The application processor of claim 4, wherein the scaling rate
calculator compares the scaling rate and an initial scaling rate
and compensates the scaling rate to be equal to the initial scaling
rate when the initial scaling rate is less than the scaling
rate.
6. The application processor of claim 4, wherein the scaling rate
calculator compensates the scaling rate based on a
current-limit-scaling rate, and wherein the current-limit-scaling
rate is a reduction ratio of the first image data that is
calculated based on an on-pixel ratio of the first image data.
7. The application processor of claim 6, wherein the scaling rate
calculator compares the scaling rate and the current-limit-scaling
rate and compensates the scaling rate to be equal to the
current-limit-scaling rate when the current-limit-scaling rate is
less than the scaling rate.
8. The application processor of claim 6, wherein the scaling rate
calculator compensates the scaling rate in proportion to the
current-limit-scaling rate.
9. The application processor of claim 1, wherein the image data
includes sub image data for each sub-pixel, wherein the stress data
includes sub stress data for each sub-pixel which includes
sub-pixel degradation information, and wherein the scaling rate
calculator selects maximum sub-pixel degradation information from a
maximum sub stress data value and calculates sub scaling rate of
the sub image data based on the maximum sub-pixel degradation
information, wherein the image processor decreases a maximum gray
scale value of the sub image data based on the sub scaling
rate.
10. The application processor of claim 1, Wherein the scaling rate
calculator periodically calculates the scaling rate with a first
period, stores the scaling rate in a memory component, and updates
the scaling rate stored in the memory component.
11. The application processor of claim 1, further comprising: a
stress calculator that generates the pixel degradation information
by accumulating input grayscale values of the first image data for
each pixel.
12. A display device comprising: a display panel that includes a
pixel; an application processor that determines a scaling rate of
first image data based on stress data that includes pixel
degradation information and generates second image data by
decreasing a maximum grayscale value of the first image data based
on the scaling rate, the first image data being received from an
external component; a timing controller that generates third image
data by compensating the second image data based on the pixel
degradation information; and a data driver that generates a data
voltage based on the third image data and transmits the data
voltage to the pixel.
13. The display device of claim 12, wherein the application
processor calculates the scaling rate of the first image data based
on the pixel degradation information and a look-up table, and
wherein the look-up table includes the scaling rate, wherein the
scaling rate is predetermined based on the pixel degradation
information.
14. The display device of claim 13, wherein the application
processor selects maximum pixel degradation information from a
maximum stress data value and calculates the scaling rate of the
first image data based on the maximum pixel degradation
information.
15. The display device of claim 14, wherein the look-up table
further includes a compensation grayscale value that is calculated
based on an input grayscale value of the first image data and the
pixel degradation information, and wherein the timing controller
generates the third image data based on the pixel degradation
information, the second image data, and the look-up table.
16. The display device of claim 12, wherein the pixel includes
sub-pixels, wherein the image data includes sub image data for each
of the sub-pixels, wherein the stress data includes sub stress data
for each of the sub-pixels which includes sub-pixel degradation
information, and wherein the application processor selects maximum
sub-pixel degradation information from a maximum sub stress data
value and calculates a sub scaling rate of the sub image data based
on the maximum sub-pixel degradation information.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
This application claims priority under 35 USC .sctn. 119 from, and
the benefit of, Korean Patent Application No. 10-2016-0006343,
filed on Jan. 19, 2016 in the Korean Intellectual Property Office
(KIPO), the contents of which are herein incorporated by reference
in their entirety.
BACKGROUND
1. Technical Field
Exemplary embodiments are directed to a display device. More
particularly, embodiments of the present inventive concept are
directed to an application processor and a display device including
an application processor.
2. Discussion of the Related Art
An organic light emitting display device displays an image using an
organic light emitting diode. An organic light emitting diode
includes a driving transistor, which provides a current to the
organic light emitting diode over time. However, degradation of the
organic light emitting diode or the driving transistor, a
phenomenon referred to as "pixel degradation", may cause an organic
light emitting display device to not display an image with a
desired luminance.
An organic light emitting display device can compensate image data,
or a grayscale value for each pixel, by calculating an amount of
pixel degradation and by adding compensation data or compensation
grayscale values for each pixel to the image data based on the
amount of pixel degradation. However, there are limitations to
compensating pixel degradation. Because the range of grayscale
values used in an organic light emitting display device is fixed,
the compensation margin, e.g., a range of compensation grayscale
values, is limited within, or less than, the range of grayscale
values. For example, when the amount of pixel degradation is
relatively large, the compensation data for the pixel may exceed
the compensation margin, and an organic light emitting display
device may not compensate the pixel degradation sufficiently or
accurately.
SUMMARY
Some exemplary embodiments provide an application processor to
ensure a sufficient compensation margin for pixel degradation.
Some exemplary embodiments provide a display device to compensate
pixel degradation with a sufficient compensation margin for pixel
degradation.
According to exemplary embodiments, an application processor
includes a scaling rate calculator that determines a scaling rate
of first image data based on stress data that includes pixel
degradation information for each pixel, where the first image data
is received from an external component; and an image processor that
generates second image data by decreasing the maximum grayscale
value of the first image data based on the scaling rate.
In exemplary embodiments, the scaling rate calculator may calculate
the scaling rate of the first image data based on the pixel
degradation information and a look-up table, and the look-up table
may include the scaling rate, and the scaling rate is predetermined
based on the pixel degradation information.
In exemplary embodiments, the look-up table may further include a
compensation grayscale value which is calculated based on an input
grayscale value of the first image data and the pixel degradation
information, where the scaling rate is greater than or equal to a
ratio of the input grayscale value to the compensation grayscale
value, and the compensation grayscale value may be equal to a
maximum grayscale value that is usable in the second image
data.
In exemplary embodiments, the scaling rate calculator may select
maximum pixel degradation information from a maximum stress data
value and may calculate the scaling rated of the first image data
based on the maximum pixel degradation information.
In exemplary embodiments, the scaling rate calculator may compare
the scaling rate and an initial scaling rate and may compensate the
scaling rate to be equal to the initial scaling rate when the
initial scaling rate is less than the scaling rate.
In exemplary embodiments, the scaling rate calculator may
compensate the scaling rate based on a current-limit-scaling rate,
where the current-limit-scaling rate is a reduction ratio of the
first image data that is calculated based on an on-pixel ratio of
the first image data.
In exemplary embodiments, the scaling rate calculator may compare
the scaling rate and the current-limit-scaling rate and may
compensate the scaling rate to be equal to the
current-limit-scaling rate when the current-limit-scaling rate is
less than the scaling rate.
In exemplary embodiments, the scaling rate calculator may
compensate the scaling rate in proportion to the
current-limit-scaling rate.
In exemplary embodiments, the image data may include sub image data
for each sub-pixel, and the stress data may include sub stress data
for each sub-pixel which includes sub-pixel degradation
information. The scaling rate calculator may select maximum
sub-pixel degradation information from a maximum value of the sub
stress data and may calculate sub scaling rate of the sub image
data based on the maximum sub-pixel degradation information. The
image processor may decrease a maximum grayscale value of the sub
image data based on the sub scaling rate.
In exemplary embodiments, the scaling rate calculator may
periodically calculate the scaling rate with a first period, may
store the scaling rate in a memory component, and may update the
scaling rate stored in the memory component.
In exemplary embodiments, the application processor may further
include a stress calculator that generates the pixel degradation
information by accumulating input grayscale values of the first
image data for each pixel.
According to exemplary embodiments, a display device includes a
display panel that includes a pixel; an application processor that
determines a scaling rate of first image data based on stress data
that includes pixel degradation information and generates second
image data by decreasing a maximum grayscale value of the first
image data based on the scaling rate, the first image data being
received from an external component; a timing controller that
generates third image data by compensating the second image data
based on the pixel degradation information; and a data driver that
generates a data voltage based on the third image data and
transmits the data voltage to the pixel.
In exemplary embodiments, the application processor may calculate
the scaling rate of the first image data based on the pixel
degradation information and a look-up table, where the look-up
table includes the scaling rate, where the scaling rate is
predetermined based on the pixel degradation information.
In exemplary embodiments, the application processor may select
maximum pixel degradation information from a maximum stress data
value and may calculate the scaling rated of the first image data
based on the maximum pixel degradation information.
In exemplary embodiments, the look-up table may further include a
compensation grayscale value that is calculated based on an input
grayscale value of the first image data and the pixel degradation
information. The timing controller may generate the third image
data based on the pixel degradation information, the second image
data, and the look-up table.
In exemplary embodiments, the pixel may include sub-pixels, the
image data may include sub image data for each of the sub-pixels,
and the stress data may include sub stress data for each of the
sub-pixels which includes sub-pixel degradation information. The
application processor may select maximum sub-pixel degradation
information from a maximum sub stress data value and may calculate
sub scaling rate of the sub image data based on the maximum
sub-pixel degradation information.
According to exemplary embodiments, an application processor
includes a scaling rate calculator that determines a scaling rate
of first image data based on stress data that includes pixel
degradation information for each pixel, the first image data being
received from an external component. The scaling rate calculator
calculates the scaling rate of the first image data based on the
pixel degradation information and a look-up table that includes a
compensation grayscale value which is calculated based on an input
grayscale value of the first image data and the pixel degradation
information.
In exemplary embodiments, the application processor may further
include an image processor that may generate second image data by
decreasing a maximum grayscale value of the first image data based
on the scaling rate; and a stress calculator that may generate the
pixel degradation information by accumulating input grayscale
values of the first image data for each pixel.
In exemplary embodiments, the look-up table may include the scaling
rate, and the scaling rate may be predetermined based on the pixel
degradation information. The scaling rate may be greater than or
equal to a ratio of the input grayscale value to the compensation
grayscale value, and the compensation grayscale value may be equal
to a maximum grayscale value that is usable in the second image
data.
In exemplary embodiments, the scaling rate calculator may select
maximum pixel degradation information from a maximum stress data
value, and may calculate the scaling rate of the first image data
based on the maximum pixel degradation information.
Therefore, an application processor according to exemplary
embodiments can ensure a compensation margin, such as a margin of
grayscale values for compensating the pixel degradation, by
determining a scaling rate of first image data received form an
external component based on stress data that includes pixel
degradation information for each pixel and by decreasing the
maximum grayscale value of the first image data based on the
scaling rate.
In addition, an application processor according to exemplary
embodiments can ensure a compensation margin for all pixels to be
compensated by determining the scaling rate of the first image data
based on the maximum pixel degradation information selected from a
maximum value of the stress data.
Furthermore, an application processor according to exemplary
embodiments can ensure an optimized compensation margin by using a
scaling rate that is based on an input grayscale that corresponds
to a time point at which a compensation grayscale value, or, a
compensated grayscale value, is saturated or at which the
compensation grayscale value has a maximum grayscale value.
A display device according to exemplary embodiments can compensate
pixel degradation with a sufficient compensation margin by
including an application processor.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a display device according to
exemplary embodiments.
FIG. 2 is a block diagram of an example of an application processor
included in the display device of FIG. 1.
FIG. 3 illustrates an example of a look-up table used by an
application processor of FIG. 2.
FIG. 4A illustrates an example of an input grayscale value
compensated based on a look-up table of FIG. 3.
FIG. 4B illustrates another example of an input grayscale value
compensated based on a look-up table of FIG. 3.
FIG. 5 illustrates an example of a scaling rate calculator included
in an application processor of FIG. 2.
FIG. 6A illustrates an example of an algorithm for calculating a
scaling rate by an application processor of FIG. 2.
FIGS. 6B and 6C illustrate examples of a scaling rate calculated
based on an algorithm of FIG. 6A.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
Hereinafter, exemplary embodiments of the present inventive concept
will be explained in detail with reference to the accompanying
drawings.
FIG. 1 is a block diagram of a display device according to
exemplary embodiments.
Referring to FIG. 1, a display device 100 includes a display panel
110, a scan driver 120, a data driver 130, a timing controller 140,
and an application processor 150. The display device 100 displays
an image based on image data, such as first image data DATA1,
received from an external component. The display device 100 may be
an organic light emitting display device.
According to exemplary embodiments, the display panel 110 includes
gate lines S1 through Sn, data lines D1 through Dm, and pixels 111,
where n and m are each an integer greater than or equal to 2. The
pixels 111 are disposed in cross-regions of the gate lines S1
through Sn and the data lines D1 through Dm, respectively. Each of
the pixels 111 can store a data signal, such as a data signal
received from the data lines D1 through Dm, in response to a gate
signal, such as a gate signal received from the gate lines S1
through Sn, and can emit light based on the stored data signal.
In some exemplary embodiments, the pixels 111 include sub-pixels.
For example, the pixels 111 may include a first sub-pixel emitting
light with a first color, such as red, a second sub-pixel emitting
light with a second color, such as green, and a third sub-pixel
emitting light with a third color, such as blue.
According to exemplary embodiments, the scan driver 120 generates a
gate signal based on a gate driving control signal SCS received
from the timing controller 140. The gate driving control signal SCS
includes a start signal or start pulse, and clock signals, and the
scan driver 120 includes shift registers that sequentially generate
the gate signal based on the start signal and the clock
signals.
According to exemplary embodiments, the data driver 130 generates
the data signal based on a third image data DATA3 received from the
timing controller 140. The data driver 130 transmits to the display
panel 110 a data signal generated in response to a data driving
control signal DCS received from the timing controller 140.
According to exemplary embodiments, the timing controller 140
controls the scan driver 120 and the data driver 130. The timing
controller 140 generates the scan driving control signal SCS and
the data driving control signal DCS and controls the scan driver
120 and the data driver 130 based on the generated signals.
According to exemplary embodiments, the timing controller 140
generates third image data DATA3 by compensating second image data
DATA2 received from the application processor based on pixel
degradation information. According to embodiments, the pixel
degradation information represents an amount of pixel degradation,
such as a degree of pixel degradation or a reduction ratio of light
emitting performance of the pixel. For example, the timing
controller 140 may calculate the pixel degradation information
based on a temperature of the display panel 110, accumulated
grayscale values for each pixel, a frame rate of the display device
100, etc.
In some exemplary embodiments, the pixel degradation information is
calculated based on the image data, such as the first image data
DATA1 or the second image data DATA2, received from the external
component. For example, the timing controller 140 or the
application processor 150 can calculate pixel degradation
information by accumulating an input grayscale value of the second
image data DATA2 or the first image data DATA1 for each pixel. The
pixel degradation information can be stored in a memory device and
be updated periodically.
In some exemplary embodiments, the pixel degradation information is
calculated based on a sensing current. For example, the display
device 100 can provide a reference voltage or a sensing voltage to
the pixels 111 and generate the sensing current by measuring a
current flowing through the pixels 111. According to an embodiment,
the display device 100 can calculate the pixel degradation
information based on the sensing current and a reference current
corresponding to the reference voltage. For example, when the
pixels 111 are degraded, the sensing current is less than the
reference current, and the pixel degradation information is
calculated based on a difference between the reference current and
the sensing current.
In some exemplary embodiments, the timing controller 140 generates
the third image data DATA3 based on the pixel degradation
information, the second image data DATA2, and a look-up table.
According to an embodiment, the look-up table includes a
compensation grayscale value which is calculated based on an input
grayscale value of the second image data DATA2 and the pixel
degradation information. The look-up table will be described in
detail with reference to FIG. 3.
According to exemplary embodiments, the application processor 150
determines a scaling rate of the first image data DATA1 based on
stress data that includes pixel degradation information for each
pixel and generate the second image data DATA2 by decreasing the
maximum grayscale value of the first image data DATA1 based on the
scaling rate. According to embodiments, the first image data DATA1
is received from an external component, and the stress data is
received from the timing controller 140 or generated by the
application processor 150. The application processor 150 can ensure
a compensation margin, i.e., a margin for compensating the pixel
degradation, by decreasing the maximum grayscale value of the first
image data DATA1 based on the stress data.
In some exemplary embodiments, the application processor 150
calculates the scaling rate of the first image data DATA1 based on
the pixel degradation information and the look-up table. According
to an embodiment, the look-up table includes a scaling rate which
is predetermined based on the pixel degradation information, or a
value equivalent to the pixel degradation information. For example,
the look-up table can represent the relationship between the pixel
degradation information and the scaling rate.
In some exemplary embodiments, the application processor 150
selects a maximum pixel degradation information based on a maximum
stress data value and calculates the scaling rate of the first
image data DATA1 based on the maximum pixel degradation
information. For reference, as an amount of pixel degradation
represented by the pixel degradation information increases, a
compensation grayscale value of compensation data also increases.
Therefore, a scaling rate calculated based on the maximum pixel
degradation information can have a minimum value or a value less
than a scaling rate value that is calculated based on other pixel
degradation information. According to an embodiment, the second
image data DATA2, which is generated based on the scaling rate, may
have a sufficient compensation margin to compensate the pixel
degradation of all the pixels 111.
In some exemplary embodiments, the application processor 150
includes an initial scaling rate and sets the scaling rate to be
equal to the initial rate when the initial scaling rate is less
than the scaling rate. According to an embodiment, the initial
scaling rate can be predetermined. That is, the application
processor 150 ensures the compensation margin to be greater than a
predetermined magnitude by selecting which of the initial scaling
rate and the scaling rate that has a smaller value.
As described above, the display device 100 according to exemplary
embodiments can ensure a compensation margin, such as a margin of
grayscale values that can compensate pixel degradation, by
determining a scaling rate of the first image data DATA1 based on a
stress data that includes the pixel degradation information for
each pixel and by decreasing the maximum grayscale value of the
first image data DATA1 based on the scaling rate.
FIG. 2 is a block diagram of an example of an application processor
included in a display device of FIG. 1.
Referring to FIG. 2, according to an embodiments, the application
processor 150 include a stress calculator 210, a scaling rate
calculator 220, a memory device or component 230, and an image
processor 240.
According to exemplary embodiments, the stress calculator 210
generates stress data DATA_S that includes the pixel degradation
information. In an exemplary embodiment, the stress calculator 210
generates the pixel degradation information by accumulating an
input grayscale value for each pixel, where the input grayscale
value is included in the first image data DATA1. For example, the
stress calculator 210 generates an accumulated grayscale value by
periodically accumulating the input grayscale value from a time in
which the display device 100 is initially driven to a current time,
e.g., with a period of four hours, and generates the pixel
degradation information proportional to the accumulated grayscale
value. According to an embodiment, the accumulated grayscale value
or the stress data DATA_S that includes the accumulated grayscale
value is stored in the memory device 230 and can be periodically
loaded or updated.
In an exemplary embodiment, the stress calculator 210 obtains or
receives the pixel degradation information from an external
component. For example, the stress calculator 210 obtains the pixel
degradation information from the timing controller 140.
According to exemplary embodiments, the scaling rate calculator 220
determines the scaling rate SR of the first image data DATA1 based
on the stress data DATA_S.
In some exemplary embodiments, the scaling rate calculator 220
calculates the scaling rate SR of the first image data DATA1 based
on the pixel degradation information and a look-up table. According
to an embodiment, the pixel degradation information is included in
the stress data DATA_S, and the look-up table may include the
scaling rate or may represent a relationship between the pixel
degradation information and the scaling rate.
FIG. 3 illustrates an example of a look-up table used by an
application processor of FIG. 2.
Referring to FIG. 3, according to exemplary embodiments, the
look-up table 300 includes the scaling rate SR_ISC and a
compensation grayscale value. According to an embodiment, the
scaling rate SR_ISC is predetermined based on the pixel degradation
information AGE, and the compensation grayscale values are
predetermined based on an input grayscale value INPUT GRAY and the
pixel degradation information AGE. The input grayscale values INPUT
GRAY may be included in the first image data DATA1 or the second
image data DATA2 and are equal to a maximum grayscale value.
As illustrated in FIG. 3, according to exemplary embodiments, the
input grayscale value INPUT GRAY increases along a vertical
direction in the look-up table 300. For example, the input
grayscale value INPUT GRAY is within a predetermined range based on
a number of data bits. For example, when there are 8 data bits, the
input grayscale value INPUT GRAY are in a range of 0 through 255,
or in a range of 0 through 256 if there are 9 bits. When there are
13 data bits, the input grayscale value INPUT GRAY is in a range of
0 through 8160, or in a range of 0 through 8192 if there are 14
bits.
According to exemplary embodiments, the pixel degradation
information AGE is in a range of 1 through 1023. The pixel
degradation information AGE is illustrated as an example in FIG. 3.
The pixel degradation information AGE is not limited thereto in
other embodiments.
According to exemplary embodiments, the compensation grayscale
value or output grayscale value corresponds to the input grayscale
value INPUT GRAY and the pixel degradation information AGE and can
be obtained through repeated experiments. The compensation
grayscale value may be represented with 13 bits.
As illustrated in FIG. 3, according to exemplary embodiments, as
the pixel degradation information AGE increases, compensation
grayscale values increase. For example, when the pixel degradation
information AGE has a value of 1, a compensation grayscale value
that corresponds to an input grayscale value INPUT of 8192 has a
value of 8192. For example, when the pixel degradation information
AGE has a value of 5 and the input grayscale value INPUT GRAY
corresponding to a maximum grayscale value has a value of 8064, the
compensation grayscale value is 8192, and input grayscale values
INPUT GRAY greater than 8064 are compensated by a compensation
grayscale value of 8192, depending on the pixel degradation
information AGE, due to limitations of the range of grayscale
values. That is, an input grayscale value INPUT GRAY greater than
8064, may not be compensated exactly or correctly. Therefore, when
the pixel degradation information AGE has a value of 5, the display
device 100 according to exemplary embodiments prevents the
compensation grayscale values from exceeding a maximum value of
8192, or to be less than a maximum value of 8192, by reducing a
range of the input grayscale value INPUT GRAY included in the first
image data DATA1 to be less than or to be equal to a range of 0
through 8064, i.e., by decreasing the maximum grayscale value of
the first image data DATA1.
In some exemplary embodiments, the scaling rate SR_ISC is less than
or equal to a ratio of the input grayscale value INPUT GRAY to the
compensation grayscale value. For example, when the pixel
degradation information AGE has a value of 5 and the input
grayscale value INPUT GRAY has a value of 8064, the corresponding
compensation grayscale value has a value of 8192. According to an
embodiment, the scaling rate SR_ISC is 0.984 (e.g., 8064/8192).
Referring again to FIG. 2, according to exemplary embodiments, the
scaling rate calculator 220 selects a maximum pixel degradation
information from a greatest stress data value and calculates the
scaling rate of the first image data DATA1 based on the maximum
pixel degradation information. For example, when the stress data
includes values in a range of 1 through 5, the scaling rate
calculator 220 selects the value 5 as the greatest of the values 1
through 5 and calculates the scaling rate SR corresponding to the
maximum pixel degradation information.
In some exemplary embodiments, the scaling rate calculator 220
includes an initial scaling rate and compensates the scaling rate
SR to be equal to the initial rate when the initial scaling rate is
less than the scaling rate. According to an embodiment, the initial
scaling rate is predetermined. For example, when a maximum
luminance of the display device 100 or the pixels 111 is 600 nits,
a desired or an initial luminance of the display device 100 is 500
nits, and the gamma is 2.2, the initial scaling rate is 0.921,
i.e., the maximum luminance of 600 nits.times.0.921.sup.2.2=the
desired luminance of 500 nits. According to an embodiment, the
display device 100 compensates the pixel degradation while
maintaining the desired luminance, i.e., 500 nits, by using the
initial scaling rate when the scaling rate SR is greater than the
initial scaling rate. On the other hand, the display device 100
compensates pixel degradation by reducing luminance using the
scaling rate SR when the scaling rate SR is less than the initial
scaling rate.
According to exemplary embodiments, the memory device 230 stores
the stress data DATA_S, the look-up table LUT and the scaling rate
SR. The memory device 230 provides the stress data DATA_S to the
stress calculator 210 in response to a request from the stress
calculator 210 and restores the stress data DATA_S, which is
periodically updated or regenerated by the stress calculator 210.
Similarly, the memory device 230 provides the look-up table LUT and
the scaling rate SR to the scaling rate calculator 220 in response
to a request from the scaling rate calculator 220. The scaling rate
SR is periodically updated and stored. When the display device 100
is driven, i.e., in a power-on state, the application processor 150
minimizes changes of image data, such as the second image data
DATA2, by using the pre-stored scaling rate SR.
According to exemplary embodiments, the image processor 240
generates the second image data DATA2 by decreasing the maximum
grayscale values of the first image data DATA1 based on the scaling
rate SR. The image processor 240 ensures a compensation margin for
compensating the pixel degradation by decreasing the maximum
grayscale values of the first image data DATA1.
As described above, an application processor according to exemplary
embodiments can ensure a compensation margin for compensating pixel
degradation by determining the scaling rate SR of the first image
data DATA1 based on stress data DATA_S that includes pixel
degradation information for each pixel and by decreasing the
maximum grayscale values of the first image data DATA1 based on the
scaling rate SR.
FIG. 4A illustrates an example of an input grayscale value
compensated based on a look-up table of FIG. 3. FIG. 4B m
illustrates another example of an input grayscale value compensated
based on a look-up table of FIG. 3.
Referring to FIGS. 3 and 4A, the horizontal axis represents the
pixel degradation information AGE, and the vertical axis represents
the compensation grayscale value OUTPUT GRAY. According to an
embodiment, the compensation grayscale value may be generated based
on a pixel grayscale value to emit light with a desired luminance.
In addition, the compensation grayscale value may be represented in
a data format of 13 bits.
A first compensation grayscale curve 421 represents a compensation
grayscale value OUTPUT GRAY that corresponds to a first grayscale
value of 6400 as a function of the pixel degradation information.
In the first compensation grayscale curve 421, the compensation
grayscale value OUTPUT GRAY increases as the pixel degradation
information AGE increases, and the rate of change of the
compensation grayscale value OUTPUT GRAY with respect to the pixel
degradation information AGE can be non-linear. In the first
compensation grayscale curve 421, the compensation grayscale value
OUTPUT GRAY has a maximum grayscale value of 8192 when the pixel
degradation information AGE has a value that is greater than or
equal to a first degradation value G1. That is, the first
compensation grayscale values OUTPUT GRAY for the first grayscale
value 6400 saturates when the pixel degradation information AGE
reaches the first degradation value G1, and does not increase as
the pixel degradation information AGE increases.
Similarly, a second compensation grayscale curve 422 represents a
compensation grayscale value OUTPUT GRAY that corresponds to a
second grayscale value 5536 as a function of the pixel degradation
information. In the second compensation grayscale curve 422, the
compensation grayscale value OUTPUT GRAY increases as the pixel
degradation information AGE increases. In the second compensation
grayscale curve 422, the compensation grayscale value OUTPUT GRAY
has a maximum grayscale value of 8192 when the pixel degradation
AGE information reaches a second degradation value G2. According to
an embodiment, the second degradation value G2 is greater than the
first degradation value G1. That is, the second compensation
grayscale value OUTPUT GRAY for the second grayscale value of 5536
saturates after the first compensation grayscale value OUTPUT GRAY
for the first grayscale value of 8600 saturates.
A third compensation grayscale curve 423 represents a compensation
grayscale value OUTPUT GRAY that corresponds to a third grayscale
value 160 as a function of the pixel degradation information. In
the third compensation grayscale curve 423, the compensation
grayscale value OUTPUT GRAY does not saturate.
For example, when the first image data DATA1 illustrated in FIG. 2
includes the first grayscale value 6400, the second grayscale value
5536, and the third grayscale value 160, the application processor
150 of the display device 100 sets the compensation margin for
compensating pixel degradation based on the input grayscale INPUT
GRAY, i.e., the first though third grayscale values 6400, 5536, and
160. According to an embodiment, a configuration for setting the
compensation margin can be complex because a compensation margin is
set for each input grayscale value.
Referring to FIGS. 3 and 4B, the horizontal axis represents the
input grayscale values INPUT GRAY, and the vertical axis represents
the compensation grayscale values OUTPUT GRAY.
A fourth compensation grayscale curve 431 represents a compensation
grayscale value OUTPUT GRAY as a function of the input grayscale
values INPUT GRAY when the pixel degradation information AGE has a
value of 30. In the fourth compensation grayscale curve 431, the
compensation grayscale value OUTPUT GRAY increase as the input
grayscale value INPUT GRAY increases, and the rate of change of the
compensation grayscale value OUTPUT GRAY with respect to the input
grayscale value INPUT GRAY is non-linear. In the fourth
compensation grayscale curve 431, the compensation grayscale value
OUTPUT GRAY saturates when the input grayscale value INPUT GRAY has
a fourth grayscale value of 7438.
Similarly, a fifth compensation grayscale curve 432 represents a
compensation grayscale value OUTPUT GRAY as a function of the input
grayscale value INPUT GRAY when the pixel degradation information
AGE has a value of 5. In the fifth compensation grayscale curve
432, the compensation grayscale value OUTPUT GRAY saturates when
the input grayscale value INPUT GRAY has a fifth grayscale value of
8032.
A sixth compensation grayscale curve 433 represents a compensation
grayscale value OUTPUT GRAY as a function of the input grayscale
value INPUT GRAY when the pixel degradation information AGE has a
value of 0. In the sixth compensation grayscale curve 433, the
compensation grayscale value OUTPUT GRAY does not saturate.
As illustrated in FIG. 4B, as the pixel degradation information AGE
increases, the saturation value for the compensation grayscale
value decreases. That is, as the pixel degradation information AGE
increases, a valid range of the input grayscale values INPUT GRAY
for the compensation grayscale value OUTPUT GRAY becomes
narrower.
Therefore, an application processor 150 of a display device
according to exemplary embodiments sets the compensation margin
based on the pixel degradation information AGE. That is, the
display device 100 sets the compensation margin based on the
maximum pixel degradation information. For example, the display
device 100 sets an optimized compensation margin for all pixels to
be compensated by decreasing the maximum grayscale values of the
first image data DATA1 to be within a range of the input grayscale
value INPUT GRAY for which the maximum compensation grayscale value
OUTPUT GRAY does not saturate.
FIG. 5 illustrates an example of a scaling rate calculator included
in an application processor of FIG. 2.
According to exemplary embodiments, as described with reference to
FIG. 1, the pixels 111 include sub-pixels. According to an
embodiment, image data, such as the first image data DATA1 or the
second image data DATA2, etc., include data for each of the
sub-pixels, and the stress data DATA_S may include sub-pixel
degradation information for each of the sub-pixels.
Referring to FIGS. 2 and 5, according to exemplary embodiments, the
scaling rate calculator 220 includes a sub scaling rate calculator
510, a minimum value calculator 520, and a selector 530. The
scaling rate calculator 220 calculates sub scaling rates
P_SR_ISC_R, P_SR_ISC_, and P_SR_ISC_B for sub-pixels.
According to exemplary embodiments, the sub scaling rate calculator
510 calculates the sub scaling rate based on a maximum sub-pixel
degradation information value selected from the sub stress data.
For example, the sub scaling rate calculator 510 selects a first
maximum sub-pixel degradation information P_AGE_MAX_TO_AP_R from a
maximum value of the first sub-pixel degradation information for
first pixels, such as pixels that emit red light, and calculates
the first sub scaling rate using a first sub look-up table
SR_ISC_LUT_R 511. According to an embodiment, the first sub look-up
table SR_ISC_LUT_R 511 is substantially the same as the look-up
table 300 described with reference to FIG. 3.
Similarly, according to exemplary embodiments, the sub scaling rate
calculator 510 selects a second maximum sub-pixel degradation
information P_AGE_MAX_TO_AP_G from a maximum value of the second
sub-pixel degradation information for second pixels, such as pixels
that emit green light, and calculate the second sub scaling rate
using a second sub look-up table SR_ISC_LUT_G 512. In addition, the
sub scaling rate calculator 510 selects a third maximum sub-pixel
degradation information P_AGE_MAX_TO_AP_B from a maximum value of
the third sub-pixel degradation information for third pixels, such
as pixels that emit blue light, and calculate the third sub scaling
rate using a third sub look-up table SR_ISC_LUT_B 513.
According to exemplary embodiments, the minimum value calculator
520 calculates or selects a minimum value from output values of the
sub scaling rate calculator 510. For example, the minimum value
calculator 520 selects a smallest sub scaling rate from the first
through third sub scaling rates.
According to exemplary embodiments, the selector 530 selects and
outputs at least one of the first through third sub scaling rates
output from the sub scaling rate calculator 510, the minimum sub
scaling rate calculated by the minimum value calculator 520, and
initial sub scaling rates P_SR_ISC_FIX_R, P_SR_ISC_FIX_G, and
P_SR_ISC_FIX_B based on an initial sub scaling rate selection
signal P_SR_ISC_FIX_EN and a minimum sub scaling rate selection
signal P_SR_ISC_MIN_EN. According to an embodiment, each of the
initial sub scaling rates P_SR_ISC_FIX_R, P_SR_ISC_FIX_G, and
P_SR_ISC_FIX_B are substantially the same as the initial scaling
rate described with reference to FIG. 2 and are predetermined.
According to exemplary embodiments, as illustrated in FIG. 5, the
selector 530 includes first through sixth selecting units or sub
selectors SEL1 through SEL6. Each of the first through sixth
selecting units SEL1 through SEL6 can be implemented as a
multiplexer.
According to exemplary embodiments, the first selecting unit SEL1
receives the first sub scaling rate and the minimum sub scaling
rate and outputs one of the first sub scaling rate and the minimum
sub scaling rate based on the minimum sub scaling rate selection
signal P_SR_ISC_MIN_EN. Similarly, the second selecting unit SEL2
receives the second sub scaling rate and the minimum sub scaling
rate and outputs one of the second sub scaling rate and the minimum
sub scaling rate based on the minimum sub scaling rate selection
signal P_SR_ISC_MIN_EN. The third selecting unit SEL3 receives the
third sub scaling rate and the minimum sub scaling rate and outputs
one of the third sub scaling rate and the minimum sub scaling rate
based on the minimum sub scaling rate selection signal
P_SR_ISC_MIN_EN.
For example, when the minimum sub scaling rate selection signal
P_SR_ISC_MIN_EN has a logic low level, the first selecting unit
SEL1 selects the first sub scaling rate, the second selecting unit
SEL2 selects the second sub scaling rate, and the third selecting
unit SEL3 selects the third sub scaling rate. For example, when the
minimum sub scaling rate selection signal P_SR_ISC_MIN_EN has a
logic high level, the first selecting unit SEL1, the second
selecting unit SEL2, and the third selecting unit SEL3 select the
minimum sub scaling rate, respectively.
According to exemplary embodiments, the fourth selecting unit SEL4
receives an output of the first selecting unit SEL1 and the first
initial sub scaling rate P_SR_ISC_FIX_R and outputs one of the
output of the first selecting unit SEL1 and the first initial sub
scaling rate P_SR_ISC_FIX_R based on the initial sub scaling rate
selection signal P_SR_ISC_FIX_EN. Similarly, the fifth selecting
unit SEL5 receives an output of the second selecting unit SEL2 and
the second initial sub scaling rate P_SR_ISC_FIX_G and outputs one
of the output of the second selecting unit SEL2 and the second
initial sub scaling rate P_SR_ISC_FIX_G based on the initial sub
scaling rate selection signal P_SR_ISC_FIX_EN. The sixth selecting
unit SEL6 receives an output of the third selecting unit SEL3 and
the third initial sub scaling rate P_SR_ISC_FIX_B and outputs one
of the output of the third selecting unit SEL3 and the third
initial sub scaling rate P_SR_ISC_FIX_B based on the initial sub
scaling rate selection signal P_SR_ISC_FIX_EN.
For example, when the initial sub scaling rate selection signal
P_SR_ISC_FIX_EN has a logic low level, the fourth selecting unit
SEL4 selects the output of the first selecting unit SEL1, the fifth
selecting unit SEL5 selects the output of the second selecting unit
SEL2, and the sixth selecting unit SEL6 selects the output of the
third selecting unit SEL3. For example, when the initial sub
scaling rate selection signal P_SR_ISC_FIX_EN has a logic high
level, the fourth selecting unit SEL4 select the first initial sub
scaling rate P_SR_ISC_FIX_R, the fifth selecting unit SEL5 selects
the second initial sub scaling rate P_SR_ISC_FIX_G, and the sixth
selecting unit SEL6 selects the third initial sub scaling rate
P_SR_ISC_FIX_B.
That is, according to exemplary embodiments, the scaling rate
calculator 220 selects the maximum sub-pixel degradation
information from a maximum value of the stress data DATA_S and
calculates or outputs a sub scaling rate corresponding to the
maximum sub-pixel degradation information. In addition, the scaling
rate calculator 220 selects the maximum sub-pixel degradation
information from a maximum value of the sub stress data and
calculates or outputs a sub scaling rate for sub image data based
on the maximum sub-pixel degradation information.
According to exemplary embodiments, as described with reference to
FIG. 5, the scaling rate calculator 220 calculate a scaling rate or
sub scaling rates for each of sub-pixels, or for each sub stress
data for each sub image.
FIG. 6A illustrates an example of an algorithm for calculating a
scaling rate by the application processor of FIG. 2. FIGS. 6B and
6C illustrating examples of a scaling rate calculated based on an
algorithm of FIG. 6A.
Referring to FIGS. 2 and 6 through 6C, according to exemplary
embodiments, the scaling rate calculator 220 of the application
processor 150 compensates the scaling rate SR_ISC based on a
current-limit-scaling rate SRdeault. According to an embodiment,
the current-limit-scaling rate SRdeault is a reduction ratio of the
first image data DATA1 calculated based on an on-pixel ratio of the
first image data DATA1. According to an embodiment, the on-pixel
ratio is a ratio of a number of activated pixels, i.e., a number of
pixels that are activated or turned on based on the first image
data DATA1, to a total number of pixels included in the display
panel 110. For example, the on-pixel ratio is a ratio of current
flowing through the pixels 11 based on the first image data DATA1
to a maximum current flowing through the pixels 111 based on a
maximum grayscale value. Generally, the display device 10 reduces
power consumption of the display device 100 by decreasing the
maximum grayscale values of the first image data DATA1 using the
current-limit-scaling rate SRdeault.
According to exemplary embodiments, as illustrated in FIG. 6A, the
application processor 150 compares the current-limit-scaling rate
SRdeault and the scaling rate SR_ISC and selects one of the
current-limit-scaling rate SRdeault and the scaling rate SR_ISC
based on a comparison result. In addition, the application
processor 150 compensates the scaling rate SR_ISC in proportion to
the current-limit-scaling rate SRdeault based on the comparison
result. For example, the application processor 150 outputs a
product of the current-limit-scaling rate SRdeault and the scaling
rate SR_ISC.
Referring to FIGS. 6B and 6C, according to exemplary embodiments, a
horizontal axis represents a load of the display panel 110, and a
vertical axis represents a scaling rate Scale Factor. According to
an embodiment, the load of the display panel 110 represents the
on-pixel ratio of the first image data DATA1 or the pixel
degradation information expressed in percentages. The scaling rate
Scale Factor represents the scaling rate SR_ISC calculated by the
scaling rate calculator 220, or the current-limit-scaling rate
SRdefualt.
According to exemplary embodiments a first scaling rate curve 621
represents a change of the scaling rate SR_ISC as a function of a
change of the load, and a second scaling rate curve 622 represents
a compensated scaling rate based on the current-limit-scaling rate
SRdefault. According to an embodiment, the compensated scaling rate
has a value equal to a value of the current-limit-scaling value
SRdefault when the current-limit-scaling rate SRdefault is less
than the scaling rate SR_ISC.
That is, according to exemplary embodiments, the application
processor 150 selects the lesser of the scaling rate SR_ISC and the
current-limit-scaling value SRdefault so that the display device
100 can be driven with a power consumption below a certain
value.
Referring to FIG. 6C, according to exemplary embodiments, a third
scaling rate curve 631 represents a change of the scaling rate
SR_ISC as a function of the load, and a fourth scaling rate curve
632 represents a compensated scaling rate based on the
current-limit-scaling rate SRdefault. According to an embodiment,
the compensated scaling rate is compensated proportionally to the
current-limit-scaling value SRdefault.
That is, according to exemplary embodiments, the application
processor 150 multiplies the scaling rate SR_ISC and the
current-limit-scaling rate SRdefault so that the display device 100
can be driven with a decreased power consumption.
Embodiments of the present inventive concept can be incorporated
into any display device, such as an organic light emitting display
device, a liquid crystal display device, etc. For example,
embodiments of the present inventive concept can be incorporated
into a television, a computer monitor, a laptop, a digital camera,
a cellular phone, a smart phone, a personal digital assistant
(PDA), a portable multimedia player (PMP), an MP3 player, a
navigation system, a video phone, etc.
The foregoing is illustrative of exemplary embodiments, and is not
to be construed as limiting thereof. Although a few exemplary
embodiments have been described, those skilled in the art will
readily appreciate that many modifications are possible in the
exemplary embodiments without materially departing from the novel
teachings and advantages of exemplary embodiments. Therefore, it is
to be understood that the foregoing is illustrative of exemplary
embodiments and is not to be construed as limited to the specific
embodiments disclosed, and that modifications to the disclosed
exemplary embodiments, as well as other exemplary embodiments, are
intended to be included within the scope of the appended claims.
Embodiments of the inventive concept are defined by the following
claims, with equivalents of the claims to be included therein.
* * * * *